1. Field of the Invention
This invention relates to devices and methods for delivering partial-thickness or full-thickness sutures in tissues endoscopically. This invention also relates to devices and methods used to minimize the strain and stress of shape memory materials.
2. Description of Prior Art
In recent years, much attention has been given to control surgical costs. One of the cost saving approaches is to accelerate the speed of recovery and shorten hospital stays after surgeries. Beyond cost savings, for the comfort and safety of patients, minimally invasive or endoscopic surgeries are becoming more and more popular. The term "endoscopic" used in this invention encompasses arthroscopic, laparoscopic, hysteroscopic and other procedures. Endoscopy is a surgical procedure which allows surgeons to manipulate instruments to view the surgical sites through small incisions in the bodies of patients.
An endoscopic surgery begins with puncturing holes through soft tissue such as skin and muscle. After the holes are made with sharp instruments, hollow cylindrical tubes called cannulas are inserted through the holes of the soft tissue. These cannulas serve as tunnels for the endoscope and surgical instruments reaching into the surgical site.
In order to minimize both the patients' trauma and potential damage to nerves, blood vessels and other tissues, it is clearly desirable to minimize the size and number of holes puncturing the patients. Take meniscal repair in the knee for example, the current arthroscopic procedure requires one hole for the arthroscope, one hole for a needle to deliver a suture and another hole for a suture-retrieving instrument to complete one suture stitch (Arthroscopic Surgery by L. Johnson, M.D.; Knee Surgery by F. Fu, M.D., et al.; Traumatic Disorders of the Knee by J. Siliski, M.D.; and Knee Surgery Current Practice by P. Aichroth, FRCS et al.). A minimum of three holes are made for the arthroscopic repair. In some cases, surgeons also require a distractor, an external fixation device which is screwed in through skin to the bones, spreading the femur from the tibia. This expands the knee joint and makes room to manipulate both the suture and the suture-retrieving instrument. Due to the tightness of joint space, often needles or instrument can accidentally scrape and damage the smooth surface of the joint, which given time, can potentially lead to osteoarthritis years after the surgery.
Arthroscopic and endoscopic suturing are done with a full-thickness technique, where sutures penetrate all the way through a tissue for each stitch. In the case of meniscal repair, the full-thickness suture repair can potentially cause long term problems, including osteoarthritis, from the constant rubbing of a very smooth joint surface to the exposed suture on the surface of the meniscus. Unless the damaged tissues can be lifted, shifted or somehow separated from crowded adjacent tissues, endoscopic procedures usually cannot be performed due to insufficient space for manipulating sutures and instruments. In these cases and others, conventional open surgery using partial-thickness suturing techniques with a curved needle, where the suture enters and loops back out without full-thickness penetration, is pursued for the repair.
Some needles (U.S. Pat. No. 5,474,565 to Trott, 1995; U.S. Pat. No. 5,222,977 to Esser, 1993; U.S. Pat. No. 5,330,491 to Walker et. al.) are designed for endoscopic surgical use. These surgical needles require multiple cannula punctures and cumbersome suture manipulation to complete each stitch.
In summary, the current instruments used in endoscopic procedures have one or more of the following drawbacks or restrictions:
(A) Increased surgical trauma due to multiple puncture wounds needed to accommodate suture manipulation and retrieving instruments. PA1 (B) Increased risk of damaging nerves, blood vessels, joint cartilage or adjacent tissues with multiple punctures and suture manipulation. PA1 (C) Lengthened surgical time. PA1 (D) Restricted by space required around and behind the surgical site. PA1 (E) Limited to full-thickness suture repair. PA1 (A) Single puncture wound needed to place, manipulate and retrieve a suture. PA1 (B) Minimal risk of damaging nerves, blood vessels, joint cartilage or adjacent tissues with single puncture and minimal suture manipulation. PA1 (C) Shortened surgical time. PA1 (D) Minimal space required around and behind the surgical site. PA1 (E) Capable in accomplishing both full-thickness as well as partial-thickness suture repair.
Another invention, U.S. Pat. No. 5,250,055 to Moore et. al., 1993, proposed a tissue- fastening technique onto bone. Moore's invention requires the drilling of two parallel holes in bone. The holes are then fitted with double barrels. A suture is attached to a non-hollow shape memory hook straightened by one barrel. As the straightened hook is pushed out of the barrel, the shape of the hook resumes and carves a tunnel in the bone reaching the second drilled hole. Another barrel houses suture retrieving tweezers to pull the suture and complete the suture loop inside the bone. The suture is then used to tie down damaged tissues onto bone. This device is not frequently used because of the large holes it makes in the bone and the difficulty of retrieving the suture with the tweezers inside the bone.
Recently, tacks (U.S. Pat. No. 5,398,861 to Green, 1995; U.S. Pat. No. 5,059,206 to Winters, 1991; U.S. Pat. No. 4,895,148 to Bays et. al., 1990) and staples (U.S. Pat. No. 5,374,268 to Sander, 1994; U.S. Pat. No. 5,154,189 to Oberlander et. al., 1992) made out of polymers and metals have been used as permanent implants to hold torn tissues in place. Very few of these devices have the holding strength of sutures. With time, some tacks and staples creep and leave gaps in the supposed closure sites. Some biodegradable tacks and staples do not last long enough for the damaged tissue to heal before disintegrating. Many of these biodegradable implants also have serious biocompatibility problems which cause inflammation and other harmful cellular interactions. For the long lasting polymeric or metal tacks and staples, there is always the nagging potential problem of device migration, which can be devastating, especially into joints and nerves.